Applicants claim, under 35 U.S.C. xc2xa7119, the benefit of priority of the filing date of Sep. 21, 1999 of a German patent application, copy attached, Serial Number 199 45 099.4, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an angle measuring device with a graduation carrier, a scanning plate and a detector arrangement on a stationary element for measuring the rotational position of the graduation carrier with respect to the scanning plate around a first axis of rotation. The present invention further relates to the use of this angle measuring device in a spindle arrangement.
2. Discussion of Related Art
Tool heads in which the tool is seated radially displaceable by an adjustment mechanism, are known for performing various production processes. This displacement takes place either by radially displaceable slides, on which the tool is fastened, or by a tool carrier, which is rotatably seated in the tool head and is eccentric with respect to the spindle axis, wherein the radial position of the tool fastened on the tool carrier with respect to the spindle axis changes by rotating the tool carrier in the eccentric bore of the tool head.
An exact position measurement is required in both cases for numerically controlling the setting of the radial position of the tool.
In tool heads with integrated slides, position measuring is performed by path measuring devices in that the scale is fastened on the slide, and the scanning unit on the tool head. A device of this type is described in DE 43 14 295 A1 and corresponding U.S. Pat. No. 5,655,422, the entire contents of which are incorporated herein by reference. This direct position measurement assures a precise detection of the radial position of the tool. In accordance with DE 43 14 295 A1, the measured position values are transmitted by infrared radiation, or inductively, from the rotating tool head to the stationary machine element or the numerical control device. Besides the actual measuring systems, separate transmission units are here additionally required, which make the arrangement more expensive, increase its structural size and makes it prone to malfunctions. This disadvantage was eliminated in the device in accordance with DE 35 26 712, and corresponding U.S. Pat. No. 4,741,230, the entire contents of which are incorporated herein by reference, in that for direct position measuring a photoelectric incremental measuring device with a scale and a scanning plate is integrated in the tool head, and the detector unit for detecting the light signals, which are modulated as a function of the position, is arranged in the stationary machine element.
Exclusively indirect measuring methods are known with tool heads in accordance with DE 22 43 734 A and DE 21 26 164 A1 along with its corresponding U.S. Pat. No. 3,740,160, the entire contents of which are incorporated herein by reference, having a tool carrier which is rotatably seated eccentrically with respect to the spindle axis. In this case, the rotating of the tool carrier is detected via the drive mechanism. This indirect measurement is erroneous, since transfer errors and the play of the interposed transmission elements (gears) are included in the measurement.
It is therefore an object and advantage of the present invention to disclose an angle measuring device, by which the angular position of a first element in relation to a second element can be detected, wherein the first element is rotatably seated eccentrically in the second element, and the second element is rotatably seated in a stationary element.
This object and advantage is attained by an angle measuring device having a graduation carrier, a scanning plate, a detector arrangement on a stationary element for measuring a rotational position of the graduation carrier with respect to the scanning plate around a first axis of rotation, wherein the scanning plate with the graduation carrier is rotatable with respect to the detector arrangement around a second axis of rotation; and the first and second axes of rotation extend parallel with respect to each other and are radially distanced from each other.
It is a further object and advantage of the present invention to disclose a spindle arrangement with an angle measuring device, wherein a direct angle measurement of a work piece or tool carrier eccentrically rotatably seated in a head is provided, wherein the head is rotatably seated in a stationary element of the spindle.
This object and advantage is attained by a spindle arrangement having a stationary machine element, a base body seated in the stationary machine element and is rotatable around a spindle axis and a workpiece carrier seated in the base body and is rotatable around a carrier axis, wherein both the spindle axis and the carrier axis extend parallel with each other and are radially distanced from each other. The arrangement further includes a scanning plate on the base body, a graduation carrier, a detector arrangement arranged on the stationary machine element for measuring a rotational position of the graduation carrier with respect to the scanning plate around the carrier axis and wherein the scanning plate with the graduation carrier is rotatable with respect to the detector arrangement around the spindle axis.
The particular advantages of the present invention lie in that the detector arrangement can be arranged stationarily, so that a direct angle measurement of elements which are eccentrically rotated with respect to each other can be performed free of malfunctions and precisely.
The invention will be explained in greater detail in what follows by means of exemplary embodiments represented in the drawings.